The present invention is directed to a continuous range dynamic sound level meter with unique features to detect, store and visually display a maximum sound level caused by a passing motor vehicle or the like which is above a predetermined noise threshold level.
In response to an increasing concern among members of the general public and the quality of the environment, many governmental authorities have enacted laws to restrict and regulate activities which may have a harmful effect on the environment. One area of official scrutiny and regulation is noise pollution. Large numbers of operating motor vehicles and other types of machinery and construction equipment may severely detract from the enjoyment of, for example, an urban neighborhood by generating excessive noise. Accordingly, many governmental authorities have enacted legislation setting noise level standards which must be observed by persons operating motor vehicles and the like. However, a problem associated with noise pollution regulation is enforcement and, in particular, the availability of a reliable, accurate and easy-to-operate device to measure noise levels and detect noise violations.
It is a primary objective of the present invention to provide a dynamic range electronic noise level meter with novel circuit means for detecting and holding a noise input which is above a threshold level set in accordance with official regulations. The detect-and-hold circuit means is initially activated by a noise level above the predetermined threshold level and operates to continuously store the maximum incoming noise level. Moreover, the circuit means compares the incoming noise level to the stored maximum level and "locks" the stored maximum level if the incoming level falls below a predetermined amount, e.g., 6 dB, with respect to the stored maximum. Additional display means are provided to visually display the stored maximum level detected by the device of the invention during a detect-and-hold sequence.
In the operation of the device, a microphone electrically connected to the sound meter is placed in close proximity to, for example, a highway or street. In this manner, the meter will detect and display the noise level in the vicinity of the highway. However, when a passing vehicle generates an impermissible noise level it will trigger the detect-and-hold circuit means so that the device will then function to continuously monitor and store the maximum incoming sound caused by the passing vehicle until the vehicle has passed and the noise level in the vicinity of the device microphone falls below a predetermined level in accordance with regulations. At that time, the circuit means will "lock" the maximum sound level caused by the vehicle and visually display the maximum reading. Accordingly, the "locked" condition represents scientific measurement evidence of a noise pollution violation.
In accordance with another feature of the invention, a beeper and indicator light are activated by the detect-and-hold circuit means at the commencement of a detection sequence to alert the operator to the presence of a possible violation. Moreover, an additional light indicator is activated at the end of a detect-and-hold sequence to signal the completion of the cycle and indicate that the visual display is a valid violation of noise pollution regulations.
For a better understanding of the above and other features and advantages of the present invention, reference should be made to the following detailed description of a preferred embodiment of the invention and to the accompanying drawings.